This invention relates generally to freeze drying equipment and, more particularly, to a method and device for determining the presence of moisture in a freeze dryer vacuum line and disabling the vacuum pump when moisture is detected.
Freeze drying is a technique well known to those skilled in the art for preserving plant and animal biological materials. A closed chamber is employed and a vacuum pump utilized to reduce the pressure within the chamber. Under the greatly reduced vapor pressure conditions, the frozen solvent in the sample sublimes, thus permitting drying of the sample without the damage to living biological material which would occur if the moisture was removed by heating the sample above room temperature. Typically, a refrigeration coil is employed in the chamber to provide a surface for accumulation of the frozen solvent vapor. When the drying process has been completed, the sample is removed and the temperature is allowed to rise above freezing so as to melt the accumulated frozen vapor from the coil. The liquid is then removed from the chamber by way of a drain line.
It is important that all liquid be removed from the collection chamber of the freeze dryer since any liquid remaining can be pulled into the vacuum pump during the next use where it will contaminate the pump oil. When this occurs the lubricating properties of the oil are greatly reduced, excess wear and corrosion is experienced, and premature pump failure may result.